A scale is a common apparatus for measuring weight of an object in daily life. With continuous development of scales and to meet different demands on different occasions, scales with multiple forms of structures have been developed, such as a steelyard, a platform scale, a counter scale, and an electronic scale. As an automated weighing device that weighs an object, the electronic scale is widely applied on various occasions such as production and family occasions due to advantages that the electronic scale is quick, accurate, automatic, and so on.
A working principle of a common electronic scale is as follows: When an object is placed on a scale pan assembly, gravity of the object is imposed on a weight sensor, the sensor is deformed, so that the impedance changes. At the same time, an excitation voltage changes, along which a changed analog signal is output. The signal is output to a corresponding control unit after certain conversion. Then, the control unit outputs a weight result to a display apparatus according to a keyboard command and a program command, so that people can intuitively obtain weight data directly from the display apparatus.
However, the common electronic scale is not convenient to carry. Hence, a card-type scale that is convenient for people to carry emerges at the right moment. However, the use scope of the card-type scale on the current market is relatively narrow and the card-type scale is usually pressed by uncontrollable external force in a carrying process. Consequently, precision of the card-type scale deviates relatively greatly after a long-time service; therefore weighing precision is affected.